netfilter: x_table: speedup compat operations

One iptables invocation with 135000 rules takes 35 seconds of cpu time
on a recent server, using a 32bit distro and a 64bit kernel.

We eventually trigger NMI/RCU watchdog.

INFO: rcu_sched_state detected stall on CPU 3 (t=6000 jiffies)

COMPAT mode has quadratic behavior and consume 16 bytes of memory per
rule.

Switch the xt_compat algos to use an array instead of list, and use a
binary search to locate an offset in the sorted array.

This halves memory need (8 bytes per rule), and removes quadratic
behavior [ O(N*N) -> O(N*log2(N)) ]

Time of iptables goes from 35 s to 150 ms.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index 742bec0..0f04d98 100644 (file)
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -611,8 +611,9 @@ struct _compat_xt_align {
 extern void xt_compat_lock(u_int8_t af);
 extern void xt_compat_unlock(u_int8_t af);
 
-extern int xt_compat_add_offset(u_int8_t af, unsigned int offset, short delta);
+extern int xt_compat_add_offset(u_int8_t af, unsigned int offset, int delta);
 extern void xt_compat_flush_offsets(u_int8_t af);
+extern void xt_compat_init_offsets(u_int8_t af, unsigned int number);
 extern int xt_compat_calc_jump(u_int8_t af, unsigned int offset);
 
 extern int xt_compat_match_offset(const struct xt_match *match);

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 16df053..5f1825d 100644 (file)
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1764,6 +1764,7 @@ static int compat_table_info(const struct ebt_table_info *info,
 
        newinfo->entries_size = size;
 
+       xt_compat_init_offsets(AF_INET, info->nentries);
        return EBT_ENTRY_ITERATE(entries, size, compat_calc_entry, info,
                                                        entries, newinfo);
 }

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 3fac340..47e5178 100644 (file)
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -883,6 +883,7 @@ static int compat_table_info(const struct xt_table_info *info,
        memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
        newinfo->initial_entries = 0;
        loc_cpu_entry = info->entries[raw_smp_processor_id()];
+       xt_compat_init_offsets(NFPROTO_ARP, info->number);
        xt_entry_foreach(iter, loc_cpu_entry, info->size) {
                ret = compat_calc_entry(iter, info, loc_cpu_entry, newinfo);
                if (ret != 0)
@@ -1350,6 +1351,7 @@ static int translate_compat_table(const char *name,
        duprintf("translate_compat_table: size %u\n", info->size);
        j = 0;
        xt_compat_lock(NFPROTO_ARP);
+       xt_compat_init_offsets(NFPROTO_ARP, number);
        /* Walk through entries, checking offsets. */
        xt_entry_foreach(iter0, entry0, total_size) {
                ret = check_compat_entry_size_and_hooks(iter0, info, &size,

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index a846d63..c5a75d7 100644 (file)
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -1080,6 +1080,7 @@ static int compat_table_info(const struct xt_table_info *info,
        memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
        newinfo->initial_entries = 0;
        loc_cpu_entry = info->entries[raw_smp_processor_id()];
+       xt_compat_init_offsets(AF_INET, info->number);
        xt_entry_foreach(iter, loc_cpu_entry, info->size) {
                ret = compat_calc_entry(iter, info, loc_cpu_entry, newinfo);
                if (ret != 0)
@@ -1681,6 +1682,7 @@ translate_compat_table(struct net *net,
        duprintf("translate_compat_table: size %u\n", info->size);
        j = 0;
        xt_compat_lock(AF_INET);
+       xt_compat_init_offsets(AF_INET, number);
        /* Walk through entries, checking offsets. */
        xt_entry_foreach(iter0, entry0, total_size) {
                ret = check_compat_entry_size_and_hooks(iter0, info, &size,

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 4555823..0c9973a 100644 (file)
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1093,6 +1093,7 @@ static int compat_table_info(const struct xt_table_info *info,
        memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
        newinfo->initial_entries = 0;
        loc_cpu_entry = info->entries[raw_smp_processor_id()];
+       xt_compat_init_offsets(AF_INET6, info->number);
        xt_entry_foreach(iter, loc_cpu_entry, info->size) {
                ret = compat_calc_entry(iter, info, loc_cpu_entry, newinfo);
                if (ret != 0)
@@ -1696,6 +1697,7 @@ translate_compat_table(struct net *net,
        duprintf("translate_compat_table: size %u\n", info->size);
        j = 0;
        xt_compat_lock(AF_INET6);
+       xt_compat_init_offsets(AF_INET6, number);
        /* Walk through entries, checking offsets. */
        xt_entry_foreach(iter0, entry0, total_size) {
                ret = check_compat_entry_size_and_hooks(iter0, info, &size,

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 8046350..ee5de3a 100644 (file)
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -38,9 +38,8 @@ MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");
 #define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))
 
 struct compat_delta {
-       struct compat_delta *next;
-       unsigned int offset;
-       int delta;
+       unsigned int offset; /* offset in kernel */
+       int delta; /* delta in 32bit user land */
 };
 
 struct xt_af {
@@ -49,7 +48,9 @@ struct xt_af {
        struct list_head target;
 #ifdef CONFIG_COMPAT
        struct mutex compat_mutex;
-       struct compat_delta *compat_offsets;
+       struct compat_delta *compat_tab;
+       unsigned int number; /* number of slots in compat_tab[] */
+       unsigned int cur; /* number of used slots in compat_tab[] */
 #endif
 };
 
@@ -414,54 +415,67 @@ int xt_check_match(struct xt_mtchk_param *par,
 EXPORT_SYMBOL_GPL(xt_check_match);
 
 #ifdef CONFIG_COMPAT
-int xt_compat_add_offset(u_int8_t af, unsigned int offset, short delta)
+int xt_compat_add_offset(u_int8_t af, unsigned int offset, int delta)
 {
-       struct compat_delta *tmp;
+       struct xt_af *xp = &xt[af];
 
-       tmp = kmalloc(sizeof(struct compat_delta), GFP_KERNEL);
-       if (!tmp)
-               return -ENOMEM;
+       if (!xp->compat_tab) {
+               if (!xp->number)
+                       return -EINVAL;
+               xp->compat_tab = vmalloc(sizeof(struct compat_delta) * xp->number);
+               if (!xp->compat_tab)
+                       return -ENOMEM;
+               xp->cur = 0;
+       }
 
-       tmp->offset = offset;
-       tmp->delta = delta;
+       if (xp->cur >= xp->number)
+               return -EINVAL;
 
-       if (xt[af].compat_offsets) {
-               tmp->next = xt[af].compat_offsets->next;
-               xt[af].compat_offsets->next = tmp;
-       } else {
-               xt[af].compat_offsets = tmp;
-               tmp->next = NULL;
-       }
+       if (xp->cur)
+               delta += xp->compat_tab[xp->cur - 1].delta;
+       xp->compat_tab[xp->cur].offset = offset;
+       xp->compat_tab[xp->cur].delta = delta;
+       xp->cur++;
        return 0;
 }
 EXPORT_SYMBOL_GPL(xt_compat_add_offset);
 
 void xt_compat_flush_offsets(u_int8_t af)
 {
-       struct compat_delta *tmp, *next;
-
-       if (xt[af].compat_offsets) {
-               for (tmp = xt[af].compat_offsets; tmp; tmp = next) {
-                       next = tmp->next;
-                       kfree(tmp);
-               }
-               xt[af].compat_offsets = NULL;
+       if (xt[af].compat_tab) {
+               vfree(xt[af].compat_tab);
+               xt[af].compat_tab = NULL;
+               xt[af].number = 0;
        }
 }
 EXPORT_SYMBOL_GPL(xt_compat_flush_offsets);
 
 int xt_compat_calc_jump(u_int8_t af, unsigned int offset)
 {
-       struct compat_delta *tmp;
-       int delta;
-
-       for (tmp = xt[af].compat_offsets, delta = 0; tmp; tmp = tmp->next)
-               if (tmp->offset < offset)
-                       delta += tmp->delta;
-       return delta;
+       struct compat_delta *tmp = xt[af].compat_tab;
+       int mid, left = 0, right = xt[af].cur - 1;
+
+       while (left <= right) {
+               mid = (left + right) >> 1;
+               if (offset > tmp[mid].offset)
+                       left = mid + 1;
+               else if (offset < tmp[mid].offset)
+                       right = mid - 1;
+               else
+                       return mid ? tmp[mid - 1].delta : 0;
+       }
+       WARN_ON_ONCE(1);
+       return 0;
 }
 EXPORT_SYMBOL_GPL(xt_compat_calc_jump);
 
+void xt_compat_init_offsets(u_int8_t af, unsigned int number)
+{
+       xt[af].number = number;
+       xt[af].cur = 0;
+}
+EXPORT_SYMBOL(xt_compat_init_offsets);
+
 int xt_compat_match_offset(const struct xt_match *match)
 {
        u_int16_t csize = match->compatsize ? : match->matchsize;
@@ -1337,7 +1351,7 @@ static int __init xt_init(void)
                mutex_init(&xt[i].mutex);
 #ifdef CONFIG_COMPAT
                mutex_init(&xt[i].compat_mutex);
-               xt[i].compat_offsets = NULL;
+               xt[i].compat_tab = NULL;
 #endif
                INIT_LIST_HEAD(&xt[i].target);
                INIT_LIST_HEAD(&xt[i].match);